Should not be C-batteries and did you put the AA back in the correct way ?

Tip - When ever I get a game and I'm not sure how things should be (as in where wires plug in ) . I always go to IPDB =Internet Pinball Data Base or Pinwiki and look at pic's . If that Comet were mine I would clean up the contacts on the original holder cut the wires to the remote holder and install Energizer Ultimate lithium AA batteries .

So with your meter - how many volts are on the yellow and black wires @ the board ?

No - we just need to know how much the remote battery pack is @ the + & - on the board . Just wondering if you removed the fuses to check with a meter ?

So on your meter I think the red lead should be plugged into the top hole that says DC v.

I think it's time to phone a friend . There must be someone near Gilbertsville , Pa. that can come over and help . That meter - you might want to donate to a museum .